<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8" />
    <title>天气案例_监视属性_简写</title>
    <!-- 引入Vue -->
    <script type="text/javascript" src="../js/vue.js"></script>
  </head>
  <body>
    <!-- 准备好一个容器-->
    <div id="root">
      <h2>今天天气很{{info}}</h2>
      <button @click="changeWeather">切换天气</button>
    </div>
  </body>

  <script type="text/javascript">
    Vue.config.productionTip = false; //阻止 vue 在启动时生成生产提示。

    const vm = new Vue({
      el: "#root",
      data: {
        isHot: true,
      },
      computed: {
        info() {
          return this.isHot ? "炎热" : "凉爽";
        },
      },
      methods: {
        changeWeather() {
          this.isHot = !this.isHot;
        },
      },
      watch: {
        //正常写法
        /* isHot:{
					// immediate:true, //初始化时让handler调用一下
					// deep:true,//深度监视
					handler(newValue,oldValue){
						console.log('isHot被修改了',newValue,oldValue)
					}
				}, 
				
				*/
        //简写
        isHot(newValue, oldValue) {
          console.log("isHot被修改了", newValue, oldValue, this);
        },
      },
    });

    //正常写法
    /* vm.$watch('isHot',{
			immediate:true, //初始化时让handler调用一下
			deep:true,//深度监视
			handler(newValue,oldValue){
				console.log('isHot被修改了',newValue,oldValue)
			}
		}) */

    //简写
    /* vm.$watch('isHot',function(newValue,oldValue){
			console.log('isHot被修改了',newValue,oldValue,this)
		}) */
  </script>
</html>
